Hi, here a quick and hopeful painless way to open the O2 sensor holes so you can fit “normal” plugs or other types of O2 sensors.
Tools needed is a 16mm 5/8 size holesaw with a hex to fit a spanner at the top and a ratchet (gear spanner to fit this 14mm or 9/16. Fit the spanner to the holesaw so it rotates in clockwise direction.
Also needed is something to use as a lever to put some pressure on the holesaw. I used a spanner with a rag taped on it so I don’t damage anything on the bike, a bit of wood will do also.
Remove the existing O2 sensors and fit the tool in the hole, take care not to damage the tread.
Apply pressure with the spanner or whatever else you use and start spannering. Keep going till it pops trough the inner pipe and remove. If you use a piece of wood as a lever it might help to put a screw in it that fits inside the spanner/holesaw to centre it.
All that’s left is do the back cylinder one and this one is a bit harder as there is less space to throw the spanner.

Now the fun part, clean the holes.... DON’T do this if you still run the original exhaust with the cat as the metal bits will end up in the cat and potentially ruin it. In that case you can take the end part off to do this! If you don’t run the original exhaust or have it removed, either fit the plugs or not but start the bike for a few seconds to clean the shit out of the exhaust... Don’t need to tell you to use earplugs or so if you have the holes open or the end pipes removed.
Let it cool down, fit the plugs, job done.
Have fun!

If you don't do anything stupid when young, you have nothing to smile about when old!

I ended up pulling the exhaust completely off the bike and grinding out the pipe with my die grinder. Your method would definitely save some time (depending on how long it took to cut through the pipe by hand).

I'll have a go at this next weekend if I can find the right cutter. Easier and maybe quicker than removing the exhaust system. But you don't say how long it took to cut through at that slow speed? A long time no doubt.

I'll have a go at this next weekend if I can find the right cutter. Easier and maybe quicker than removing the exhaust system. But you don't say how long it took to cut through at that slow speed? A long time no doubt.

Actually less than 5 minutes, I was surprised myself. For the rear cylinder I tought I was in for the long haul but it took about the same. Hardest thing is to keep it more or less centered.
Have fun!

If you don't do anything stupid when young, you have nothing to smile about when old!